Plasma display devices using PDPs (Plasma Display Panels) have the advantage that thinning and larger screens are possible. In the plasma display devices, images are displayed by utilizing light emission in cases where discharge cells composing pixels are discharged. As light is thus emitted, heat is generated on a glass surface composing the PDP, so that the higher the luminance of-an image. becomes, the larger the amount of heat generation becomes. Therefore, the temperature of the glass surface is raised. In the worst case, the glass surface is damaged.
In order to solve the above-mentioned problem, an example of a conventional display device is a display device disclosed in JP-A-11-194745. In the display device, the whole surface of a display screen is divided into a plurality of blocks, temperature estimated values are calculated with respect to all the blocks, and the maximum value of the calculated estimated temperatures is compared with a reference temperature to produce a luminance correction coefficient. The luminance of the display screen is controlled by the luminance correction coefficient.
A display on which an image is displayed is generally fixed in its outer periphery. Damage to the display caused by the rise in the temperature with the increase in the luminance may occur in the vicinity of the outer periphery of the display in most cases. That is, the damage to the display depends on the temperature difference rather than the maximum temperature. Generally, the temperature difference between the outer periphery of the display where no heat is generated and the outer periphery of the display screen of the display where heat is generated is the largest. The display may be damaged by thermal stress created by the temperature difference in many cases.
In the conventional display device, however, only when the maximum value of the estimated temperatures reaches not less than the reference temperature, that is, when the temperature of any portion on the display screen exceeds its certain upper-limit value, the luminance is controlled.
Therefore, the luminance cannot be always controlled when excessive thermal stress is exerted on the outer periphery, which is most easily damaged, of the display, thereby making it impossible to reliably prevent the display from being damaged.
In the conventional display device, the whole of the display screen is divided into a plurality of blocks, and the estimated temperatures are calculated with respect to all the blocks. Accordingly, operation processing becomes complicated, and long time is required to perform the operation processing. Particularly in recent years, it has been desired to make a display image highly precise. The number of pixels composing the display screen, that is, the number of discharge cells has tended to be increased. In this case, the above-mentioned operation processing has increasingly become complicated, and the processing time is lengthened.